Concentric indicator, filar geared electrical measuring instrument



Aug., i, H950 F. X. LAME CONCENTRIC INDICATOR, FILAR GEARED ELECTRICAL MEASURING INSTRUMENT Filed Feb. 27, 1947 atenteci ug. 1V, 195,0

CON CENTRIC INDICATOR, FILAR GEARED ELECTRICAL MEASURING INSTRUMENT Francis X. Lamb, East Orange, N. J assigner to Weston Electrical Instrument ICorporation, Newark, N. J., a corporation of New Jersey Application February 27, 1947, Serial No. 731,2'i3

2 Claims.

, This invention relates to measuring instruments and in particular to those ofthe sensitive electrical type employing afrctor such as a `coil which rotates in an electro-magnetic leld 1n accordance with the magnitude of the coil current.

An object of the invention is to provide a dual element electrical measuring instrument in which the relative angular displacement of the two electro-sensitive elements may be instantly and most accurately compared on a common scale by means of a pair of concentrically mounted pointers. Another object is to provide an electrical measuring instrument having dual moving systems that is compact and of small overall dimensions but which nevertheless affords considerable amplification of the angular displacement of the electro-sensitive `element of each moving system as read on the instrument scale thereby making it much easier to compare the relative positions -of the pointers and also improving the accuracy of the scale reading. Another object is to provide an electrical measuring instrument having a pair of independent moving systems of the extremely sensitive type such as a coil or vane and the like operating in a magnetic eld and a pointer driven thereby, theinstrument pointers being mounted concentrically for rotation over a common scale and coupled to the coils through gearing which permits an ampliiied angular displacement of the pointers with respect to the coils. i

Yet another object is to provide a dual element indicating device of the electrical instrument type that includes a pair of concentrically mounted pointers which work over a common scale, the pointers being driven respectivelyfrom separate electro-sensitive elements through angular motion-multiplying gearing having `low transmission losses of the general type described in my prior U. S. Patent No. 2,313,444, `issued March 9, 1943, whereby the relative current inputs to the two sensitive elements may be instantly compared over a large deflection angle on the same scale.

These and other objects and 'advantages of the invention will become more apparent from the following detailed description when considered with the accompanying drawings which illustrate an application of the principles of the invention to a dual element electrical speed indicator for use on twin engine aircraftiand the like where it is desired to indicate and compare therelative speeds of the two engines. However the illustrated embodiment is to be understood as typical only of the many possible different applications to which theimproved instrument mechanism may be put, all of which are intended to be embraced in the scope of the claims appended hereto. In the drawings, Fig. 1 is an end elevation of a preferred construction of the multiple element instrument; Fig. 2 is substantially a longitudinal vertical section with certain of the working parts shown in elevation for clearness; and Fig. 3` is an enlarged detail showing the construction by which the pointers are concentrically mounted. Referring now to the drawings, it is seen that the multiple element instrument is comprised of a pair of instrument mechanisms Il` and 2 mounted vertically one above the other andsupported within a casing 3. The mechanism designated I is comprised of a wire wound, substantially rectangular, coil type rotor 4 mounted upon a staff 5 which is received at each endin adjustable jewelled bearings 6 and E'. A cylinf drical core 1 lies within coil 4` and the latter rotates within` the magnetic field set up across poles 8a, 8b of a double permanent magnet as` sembly 8. 4 A generally `Y-shaped member 9 is secured intermediate its ends on the staff 5, and spanning the downwardly extending outer ends of the arms of this member which define an included angle of approximately 90, is a gear sector Ill having internal teeth I0a. An adjustable weight II threaded onto the base end of the Y member 9 is provided` to balance the member about the axis of stai5. i ,13; `Giear sector Il) is -meshed with a fllar gear I2 which includes spaced end anges I3 and re,-v silient tooth elements I4 of silk or a synthetic resin such as nylon stretched between the ilanges. As shown clearly in the enlarged detail view of Fig.` 3, lar gear I2 is carried by a shaft I5 which extends through the end flanges I3, the

" shaft being hollow throughout most of its length to reduce the mass of the instruments moving system. Plugs I6 anchored iniopposite ends `of shaft I5 each carryone end of staffs I'I`, I8 ex` tending axially in opposite directions. Staff Il is received in an adjustable jewelled bearing Iii carried by a vertical support while staff I8 terminates in a press t within one end of an axially aligned shaft 2I on which is mounted a balanced pointer 22. A stub staff 23 extending axially from the opposite end of shaft 2I is received in an adjustable jewelled bearing 24 supported by a bridge 25. The latter is secured by studs 2B to a circular plate 121 that forms a backing for scale plate 28 having graduations 23, and hence it will now be evident that as coil 4 is displaced angularly in accordance with the current sent through it, such motion will be transmitted via sector gear III to iilar gear I2 causing the latter and hence staffs I8, 2l and pointer 22 to rotate over scale plate 28.

The limit of the angular displacement of coil 4 in the illustrated construction is somewhat less than 90. However, due to the angular motionmultiplying lar and sector gear arrangement, the angular displacement of pointer 21Z^may exceed 360 depending upon the ratio of the gear transmission. In the illustrated. construction, the ratio of angular displacement of lar gear I2 to that of coil 4 is such that pointer 22 will be displaced approximately 330 from zero position for full deiiection off coil 4S.

The other and indepe-ndently` operated instru'- ment mechanism 2 as shown in- Fig. 2 isy similar to mechanism I-l and includes a rectangular coil 3U'v disposed below coil 4' and similarly mounted on a` staff 3I= receivedv at each end inr adjustable jewell'ed bearings 32, 32:. A stationary. core 34 is supporti-ad` within coil Bilanci the latter rotates on its axis with-inthe magnetic eld set up across two other poles 8c, 8d of-V the other half of the permanent magnet assembly: 8.

A secondy V-sh-aped member 35 havingl an internally toothed gear sector 361 and' balance weight 31T is secured to staff 3l for rotation therewith. Crearl sector 36 extending upwardly froml staff' illy is=meshed with a second lar gear 31 ofthe same construction as gear I2.- having resilient tooth strandsI 3811 secured at their opposite ends to flanges 39.

Referring again to Fig. -,ri'llar gear 3'! is` carriedA bya hollowshaft 4I? that extend's through the endflangesv 33` andfwhich` is in` turn mounted concentrically onv stai I8',A by` ring bearings.y lII, 42 locatedv in opposite ends` of shaft 43. AA sleeve Siforming an axial extension ofi shafttlif carries apointer- 44- and hence-thispointer rotatesv as the se-ctorgear Slil drives iilar gear 3-'I upon displace ment of coil 30.

The pairs off poles 8a-8b and 8c-8d` of the magnet assembly.I 8 are sopoled and the. relative directions of current. flow through the coils 4 and 301 areA so chosen that the coils rotate in the same relativel direction, which is clockwise when viewed fromy the front elevation of Fig. l. HenceA pointers 22. and 44 will both rotate in a clockwise direction fromathelrzero scale position in accordance with the magnitude ofthe respectivecurrents sent through their associated coils 41and30. It is apparent the direction of current flow throughV one of the coils can be reversed whereby the pointers will rotate in opposite directions to provide readings. on either side of a zero positionlocated. at, say; the midpointof the scale range.

In the illustrated embodimenty ofthe inven tion, it is contemplated that the dual. pointer instrument Will be used ina dual engine aircraft. for indicating the speedinrevolutions. per minutev of; a pair of engines. Hence as shown in Fig. 1, the dial scale is graduatedinstepsof 50B; Pz. M.

from 0 to 3200, the pointers each having an angu lar travel of 330 from the zero speed position. The circuits for supplying speed-responsive voltages to the respective instrument mechanisms I and 2 are not illustrated as they form no part of the invention and preferably conform to current practice in the electrical tachometer art.

It is common knowledge that the moving coils of the permanent magnet type of electrical measuring instrument which has been described are most sensitive and have a very lou7 driving torque. The lar gearing transmission associated with each of the coils 4 and 30- provdes however a most desirable amplification of the coil displacement without imposing any substantial loading on the coils and hence the respective angular motions of coils 4;.y and 30 are translated to the pointers 22 and' 4'4 with a high degree of pre cision.

The iilar gears I2 and 31, and their meshed sector driving gears, II) and 36 are preferably made in accordance with the construction described in my copending application Ser. No. 700,574, led October l, 1946, now Patent No. 2,502,160, issued March. 28, 1950. However, the gea-r transmission may beas described my previously granted; U. S.. Patent No.4 2;,3.l3,44.4 issued March`r 9,4 1943..

In conclusion it'v willbe evident that the. dual movement indicating,l instrument construction described whereirhtheV movements are-mountedin vertical alignment with the driver. gear sectors ext-endingA towards each other` and, meshed; with axially, i alignedL filar` gearsI results; in; a. most. com.- pact instrument of small over-all dimensinnsl that. makes it most. desirable,v especially when used. on aircraft instrument panelhoards where spacefis aprirne factor in-.view of the large number of indicating instruments .on thev board. The invention, however, is o bvously'not. to.I be limited tospeedindicators. but can beappliedequally as well for comparing. the relative magnitudes,` ois` other measured variables such. as temperatureny pressure, lquid-leveletc. Also-V it will be understood that various changes in the. construction and arrangement. of parts of: the; illustrated ein.- bodiment may be madeI without departing from the spirit and' scope of the appended claims.,

I claim: y

1.. In a dual indicator hype.4 electrical. measuring, instrument the combination comprising a pair of. spaced parallel movements eachnfwl'iiclr includes arotor and an associated magneticY eld system, a pair oi. telescopcally arranged and-,inf dependently rotatable pointer shafts; located, be.-l tween said movements and arranged@ parallel with the rotor. elements. thereo, a filer gear: secured. upon eachshaft, acounterbalanced driver gear associated withV each rotor anddriventhere by, saidy driver gears-being;` gear sectors extending towards each other; and.: meshedf respectively with-V saidiilar gears and. havingv a. pitchdiameter substantially greater than. that. of; said.. lar: gears,` a pointer attached to each:` shait, and, a. scale* plate over which said pointers are angularlydisfplaced.

2. In a duallindicator typeelectricalmeasur. ing instrument, the` combination comprising, a: pair of spaced parallel movementszeaoh of which includesarotor and an: associated magnetcfield system, a concentric; dual pointer shaft system.. journalled in jewelledl bearingsthefshafts'ofsaid systemJ being telescopically arranged andy inde-A pendently rotatable, saidl shaft system being- 10. cated between` said movementsk and arranged;-

5 parallel with the rotor elements thereof, a fllar UNITED STATES PATENTS gear secured upon each shaft, a counterbalanced Number Name Date driver gear associated With each Said 101201' and 600 931 Weston M313 22 1893 driven thereby and meshed respectively With Said 1 518'332 Kloneck Dec g1 1924 lar gears, said driver gears being internally 5 1960241 Deerwester May 29 1934,V toothed gear sectors extending towards each n other and embracing the lar gear meshed there- FOREIGN PATENTS with and having a pitch diameter substantially Number Country Date greater than that of said lar gears, a pointer at- 12,527 Great, Britain May 29|, 1913 tached to each shaft, and a scale plate over 10 59,592 Austria June 10, 1913 which said pointers are angularly displaced. 256,447 Germany Feb. 11, 1913 FRANCIS X. LAMB.

REFERENCES CITED The following references are of record in the 15 file of this patent: 

